Fixed- and especially mobile- networks, such as Global System for Mobile communications (GSM), General Packet Radio System (GPRS) or Universal Mobile Telecommunication System (UMTS) are constantly evolving. GSM/GPRS and UMTS networks today offer both Circuit Switched (CS) connectivity and Packet Switched (PS) connectivity. The PS end-to-end connectivity with its capabilities for transmission of a wide range of data types may be used for offering multimedia services such as image, music and video transfer. The CS connectivity provides a reliable link between two User Equipment by means of one or more trusted network-nodes with a reliable and defined Quality of Service (QoS).
Combinational networks, where two or more links of different type to one or more User Equipment are established, are capable to deploy both CS- and PS-connectivity to a user equipment, thereby enabling services which perform their activity by PS-communication sessions, denoted as PS-sessions and CS-communication sessions, denoted as CS-calls.
As to benefit from this form of service combination, user equipment are required that are capable of handling a CS-call and a PS-session simultaneously. Multi Radio Access Bearer (RAB) terminals for UMTS and Dual Transfer Mode (DTM) terminals for GSM/GPRS networks will be available; these types of terminals provide support for simultaneous CS- and PS-connectivity.
Today, conversational voice cannot be delivered over PS bearers to the end user, due to e.g. insufficient capacity in the Radio Access Networks in operation and therefore existing CS bearers are used for delivering conversational voice. In the future, it may be possible that a single PS bearer is used for conversational voice and multimedia. Nevertheless, DTM terminals today, and possibly UMTS user equipment in the future, will deliver support for simultaneous CS- and PS-connectivity.
In order to give the end-user the look and feel of a single service, although the service may be composed of various CS- and PS-domain services, deployed in the CS-network and the PS-network respectively, it is desirable to determine and deploy some form of relation between ongoing CS-calls or CS-calls that are to be established and the ongoing or to be established PS-session(s).
Some examples of said desired to be determined relation:    1) It should be possible to provide the user of a DTM phone with a rich alert, i.e. as opposed to a simple audio-only alert, as common at a CS-call, the user gets a visual rendering as well. This visual rendering could contain e.g. a photograph of the calling party, the calling party's name or the priority of the call. As far as the receiving party is concerned, it does not matter whether the CS-call was made from a user equipment with PS capabilities or just a “normal” (capable of CS-calls only) phone. In the latter case, an entity in the network, e.g. an Internet protocol Multimedia Subsystem (IMS) may have generated the “rich” part of the call. In this case the alert at the receiving phone, initialised by a CS-network, is related to the visual rendering at the receiving phone    2) To ease user interaction, it should be possible for parties involved in a CS-call to be able to specify with ease (e.g. with a single click of a button) that a picture, video or file shall be sent to the party with which a speech communication is ongoing (i.e., the current CS-call partner). In this case the ongoing CS-call is related to the existing or new PS-session required for sending said data portion.    3) If a CS-call is established between users A and B, it would be desirable to have the possibility to charge the PS-session (e.g. exchange photos, share whiteboard, etc.) between the users A and B with a different tariff than normal (i.e. as opposed to the tariff that applies to the PS-session in isolation), and present the user a single bill. In this case the charging of the PS-sessions is related to the charging of the CS-call as to present said user a single bill, which is traditionally related to CS-calls only.    4) During an ongoing CS-call to a helpdesk or an assistance service, it would be desirable for the helpdesk to have the possibility to send additional multimedia (pictures/video with text) that illustrates a solution to a problem. In this case the ongoing CS-call is related to a PS-sessions where the additional multimedia information is exchanged.    5) It would be desirable to influence a QoS of a PS-session when a CS-call is ongoing. For instance video streaming during the CS-call, comprising a voice call, is handled with a higher priority. Here it is required that the relation between the CS-call and the PS-session has to be known by the user equipment, the network, or by both, as to influence the QoS.
In all these examples stated above, it is desirable to determine a relation between the CS-call and the PS-session in such a way, that the relation is made known in a simple and reliable way without any remarkable delay towards the user equipment or the network. Furthermore it should be ensured towards the user that any costs generated for the PS-session are billed in a trusted way in relation to his/hers CS-call.
The problem that the invention seeks a solution to, is formulated as a two-part problem.
A first part of the problem deals with: “How to find the relation between the CS-call and the PS-session?” More specifically, how can a service determine whether or not a latest service trigger belongs to an ongoing service? This needs to be resolved under different circumstances, namely: the latest service trigger concerns a CS- or a PS-service, the ongoing service itself is a CS- or a PS-service, and finally the service may be resident in the user equipment or in the network. This first part of the problem is defined as how to provide correlation means for correlating the CS-call with the PS-session.
A second part of the problem deals with “How to provide an incentive to start a process for finding the relation between the CS-call and the PS-session?” More specifically, how should an entity indicate, or suggest, or point-out that the CS- and PS-services are correlated? This second part of the problem is defined as how to induce a correlation between a CS-call and a PS-session.
Furthermore it should be desirable that the correlation induction takes place at the communication means of the user or by an intercepting service. Any solution to said problem must fulfill the following requirements:                The correlation between the CS-call and the PS-session should not place extra requirements on the user, i.e. the user should be able to spontaneously place the CS-call or start-up the PS-session, not knowing whether he/she would initiate another, related CS- or PS-service later during that call or session.        Any solution found should work on various networks, even if a mix of various networks is deployed with different protocols. This is applicable when a call crosses a Gateway node between two networks, especially when these two networks are heterogeneous, e.g. GSM & TDM or GSM & PSTN/ISDN etc.        